It’s all in the details: new study does NOT show that ‘crying it out’ does no harm.
Solid research has been published into the effect of sleeptraining on babies. Solid, because it is a well designed study in which not only the effect on sleep itself was measured but also on stress in both mother and child (cortisol) and bonding. And the outcomes do show that the sleepinterventions did not increased measurable stress in the baby, did not disrupt bonding and had possible positive effects for both mother and child.
So far the abstract. But. Of course there is a but. The devil is in the details.
The detail ‘age’ in this case. This study was done with babies age 6 – 16 months.
And everyone who has ever been around human babies will realise that a baby in the first months of life is much more vulnerable than that same baby after the first half year. Humans develop spectacularly in their first half year and in that development consistent care, bonding and contact are vital.

A human is extremely vulnerable in the first months of life. Even when compared to other primates human babies need constant care and security. We need to be offered food, warmth, physical support and contact. In the first 3 – 6 months of life the human baby cannot hold onto a carer, can not initiate fysical contact and can communicate with sounds only in a limited range.
Sleep itself changes in babies in the first months of life. A day-night pattern only develops after +/- 2 months. And it develops in close contact with the environment: the adults looking after the baby.
All in all I sincerely hope the researchoutcome will be represented correctly in the common press: Sleeptraining AFTER 6 MONTHS does not increase stress.
But I expect headlines like ‘Crying it out does no harm’. Why? Because that would be so convenient in a society where the trend towards babies seems to be that they should be as silent as possible as long as possible as soon as possible during the night.
That conclusion is not warranted based on this research.
After 6 months there is now some indication to lovingly (my addition) teaching children to sleep longer or at least wake their parents less a night. Let us please go gently and comfort them their first months of life.